Secure envelope and method for securing information

ABSTRACT

A windowed envelope is disclosed comprising: a first panel with an interior and an exterior side; a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope; and a flap for sealingly adhering to an exterior surface of the first panel. The flap has an interior and an exterior side and is attached to the second panel at an edge of the second panel opposite the closed edge portion. The envelope comprises thereon an adhesive layer on the interior side of the flap comprising an adhesive; wherein a non-transparent window is located on the first panel or the second panel. The window comprises a reducible dye and a microencapsulated reducing agent, which is adapted to irreversibly change to a transparent window upon heating the non-transparent window to a temperature above room temperature.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention disclosed herein relates to envelopes and, more particularly, to secure envelopes and methods for securing information to preserve confidentiality and prevent fraud.

2. Background Information

Voting for candidates in the United States is typically performed using mechanical voting machines at predetermined polling places. However, if an individual is unable to go to the polling place at which he or she is registered, an absentee ballot may be used to allow the individual to cast the vote. Typically, the user of an absentee ballot selects his or her choices on a ballot and returns the ballot to the election official by mail.

In order for the ballot to be counted, it must comply with the applicable election laws and be valid. For absentee ballots to be valid, for example, the ballot must have been created, i.e. completed by the voter, in a timely manner and submitted for return to the election officials. The election officials also verify that the voter is properly registered in that voting district and that they have not already voted in the election.

In the usual absentee voting process, the voter casts his/her vote on the ballot, inserts the ballot in return envelope, which is addressed to the Registrar Office of the corresponding country, and appends his/her signature on the back envelope besides his/her identification. At the Registrar's Office, a voting official can compare the signature with the one retrieved from the registration file and decide whether the vote can be considered authentic.

A new law in the state of Washington is requiring the signature to be hidden from sight. A goal of the law is to protect again easy imaging of the signature with, for example, a hand scanner or digital camera, for later impersonation or other fraudulent purposes.

Moreover, in many voting by mail systems, the filled ballot is enclosed in a “secrecy envelope” located inside the return envelope, so that during the opening of the return envelope, where the identity of the voter can still be seen, the filled ballot is still protected and no link between the voter and the vote can be made. This process demands one more step to the voter (e.g., inserting his/her vote in the secrecy envelope) and one more envelope opening process at the counting point. Thus, important concerns include protecting the voter's privacy and prevention of fraud.

Accordingly, in a voting by mail system there is a desire to hide the user's personal and confidential information from the vote that was placed in order to protect the user's privacy. There is also a desire for secure envelopes for use in such systems to preserve confidential information and prevent fraud. There is a further desire to hide information in other secure envelopes.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a windowed envelope is disclosed comprising: a first panel with an interior and an exterior side; a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope; and a flap for sealingly adhering to an exterior surface of the first panel. The flap has an interior and an exterior side and is attached to the second panel at an edge of the second panel opposite the closed edge portion. The envelope comprises thereon an adhesive layer on the interior side of the flap comprising an adhesive; wherein a non-transparent window is located on the first panel or the second panel. The window comprises a reducible dye and a microencapsulated reducing agent, which is adapted to irreversibly change to a transparent window upon heating the non-transparent window to a temperature above room temperature.

In accordance with another aspect of the invention, a method of detecting information located inside a closed envelope without opening the envelop is disclosed. The method comprises: providing a windowed envelope comprising: a first panel with an interior and an exterior side; a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope; and a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion. The envelope comprises thereon an adhesive layer on the interior side of the flap comprising an adhesive; wherein a non-transparent window is located on the first panel or the second panel. The window comprises a reducible dye and a microencapsulated reducing agent, which is adapted to irreversibly change to transparent upon heating the window to a temperature above room temperature; wherein information is located in the envelope behind the window. The method further comprises heating the window to a temperature above room temperature, wherein the window irreversibly changes from non-transparent to transparent thereby exposing the information located in the envelope behind the window.

In accordance with another aspect of the invention, a windowed envelope comprises: a first panel with an interior and an exterior side; a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope; and a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion, the envelope comprising thereon an adhesive layer on the interior side of the flap comprising an adhesive. A non-transparent window is located on the first panel or the second panel. The window comprises a thermochromic material, which is adapted to change to a transparent window upon heating the non-transparent window to a temperature above room temperature.

In accordance with a further aspect of the invention, a method of detecting information located inside a closed envelope without opening the envelop comprises: providing a windowed envelope comprising: a first panel with an interior and an exterior side; a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope; and a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion. The envelope comprises thereon an adhesive layer on the interior side of the flap comprising an adhesive; wherein a non-transparent window is located on the first panel or the second panel. The window comprises a thermochromic material, which is adapted to irreversibly or reversibly change to transparent upon heating the window to a temperature above room temperature; wherein information is located in the envelope behind the window. The method further comprises heating the window to a temperature above room temperature, wherein the window changes from non-transparent to transparent thereby exposing the information located in the envelope behind the window.

In accordance with another aspect of the invention, a method of detecting whether contents of a closed envelope have been read or tampered with comprises the steps of: providing a sealed, windowed envelope. The envelope comprising: a first panel with an interior and an exterior side; a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope; and a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion. The envelope comprising thereon an adhesive layer on the interior side of the flap comprising an adhesive; wherein a window is located on the first panel or the second panel, the window comprising at least two layers each comprising a thermochromic material, wherein one of the layers is transparent at room temperature and another layer is non-transparent at room temperature. The method further comprising then sequentially, heating the layers to a temperature above about 50° C. and less than about 100° C., wherein both layers become transparent; and heating the layers to a temperature above about 100° C., wherein one of the layers is non-transparent and the other layer is transparent. The method may also further sequentially comprise: allowing the layers to reach about room temperature wherein both layers become non-transparent; heating the layers to between about 50° C. and less than about 100° C.; and heating the layers to a temperature above about 100° C. wherein one of the layers is non-transparent and the other layer is transparent.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and other features of the present invention are explained in the following description, taken in connection with the accompanying drawings, wherein:

FIG. 1 is a perspective view of an envelope, in accordance with an embodiment of the invention;

FIG. 2 shows another envelope, in accordance with an embodiment of the invention;

FIG. 3 shows an envelope having a window, in accordance with an embodiment of the invention;

FIG. 4 shows another view of envelope having a window before heating, in accordance with an embodiment of the invention;

FIG. 5 shows the envelope of FIG. 5 after heating, in accordance with an embodiment of the invention;

FIG. 6 shows a multilayer film 42, in accordance with an embodiment of the invention;

FIG. 7 shows a window incorporating IR or microwave absorbents, in accordance with an embodiment of the invention;

FIG. 8 shows the state of an envelope 10 before heating the window, which comprises a thermochromic material, to a temperature above room temperature to transform the window from non-transparent to transparent, in accordance with an embodiment of the invention;

FIG. 9 shows the envelope of FIG. 8 after heating, in accordance with an embodiment of the invention;

FIG. 10 shows a multilayer film 42 comprising heat insulating layers 44, in accordance with an embodiment of the invention;

FIG. 11 shows window 36 incorporating IR or microwave adsorbents, in accordance with embodiments of the invention; and

FIGS. 12( a)-(b) shows an approach employing both irreversible and reversible thermochromic materials, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a schematic illustration of a first embodiment of the invention. Although the invention will be described with reference to the embodiments shown in the drawings, it should be understood that the invention can be embodied in may alternate forms of embodiments. In addition, any suitable size, shape or type of elements or materials could be used.

There is illustrated in FIG. 1 an envelope 10, in accordance with one embodiment of the invention. Envelope 10 may be formed in any desired shape and size. For example, envelope 10 may be formed from a single sheet of material or multiple sheets of material. In the embodiment shown in FIG. 1, envelope 10 includes a first panel 12 with an interior side 14 and an exterior side 16 and a second panel 18 attached to the first panel 12 to define an interior portion 20 of the envelope 10. The envelope 10 has opposite side edges 22 and a closed edge portion 24 to provide access to the interior portion of the envelope 10.

In the embodiment, shown, in FIG. 2, the first panel 12 comprises a plurality of folded flaps 6, which are folded inwardly to produce a general, conventional V-shaped configuration 4.

As shown in FIGS. 1 and 2, envelope 10 may also include a flap 28 for sealingly adhering to the exterior side 16 of the first panel 12. The flap 28 has an interior side 30 and an exterior side 32 and is attached to the second panel 18 at an edge of the second panel 18 opposite the closed edge portion 24. The interior side 30 also typically comprises an adhesive layer 34, which comprises a suitable adhesive for sealing the flap 28 to the exterior side 16 of envelope 10. Suitable adhesives include, for example, conventional envelope gumming, glue, latex based adhesives, etc.

Envelope 10 may be made out of any suitable material in any suitable thickness. Typically, envelope 10 is constructed out of paper or cardboard. A material thickness of about 0.0001 inches or greater is also typical. Envelope 10 may be constructed of a single layer or of multiple layers.

As also shown in FIG. 3, envelope 10 comprises a non-transparent window 36 in any suitable shape, size and location on envelope 10. Window 36 may comprise a thin polymeric film typically between about 0.0001 and about 0.01 inches in thickness comprising a reducible dye and a microencapsulated reducing agent either as part of an ink vehicle overcoated on the conventional window film, or in the conventional polymeric matrix film of the window itself.

The reducible dye may include any suitable dye of desired color. Examples of suitable reducible dyes include methylene green, methylene blue and rezasurin. These dyes can become colorless upon chemical reduction or alkaline conditions.

Examples of suitable microencapsulated reducing agents include bleach, chemical bases such as NaOH, and inorganic and organic reducing agents. U.S. Pat. No. 4,126,717 discloses a suitable method for the encapsulation of bleaches. The contents of this patent are incorporated by reference.

As described in the afore-referenced patent, for example, granulated material to be encapsulated is charged into a rotating drum mixer, molten, solvent free combinations of selected fatty acids and waxes are sprayed onto the tumbling granules. The molten combination is sprayed in a finely divided state and at a rate which prevents excess agglomeration and results in the application of a coating of the combination on the particles.

If an overcoat is employed, the polymeric film of window 36 may comprise any suitable, conventional polymeric or plastic film. In this embodiment, the reducible dye and microencapsulated reducing agent may be incorporated into a suitable ink composition and deposited on the polymeric film. More particularly, inkjet, flexographic, screen and lithographic printing could be used to print on the envelope film. For example, in inkjet printing the formulation may contain the reducible dye (e.g. 0.25 to 5%) and the microencapsulated agent (with a concentration range larger than the reducible dye) within an inkjet vehicle known in the trade.

Alternatively, the reducible dye and microencapsulated reducing agent may be incorporated into the polymeric matrix of the film itself by mixing techniques. More particularly, this matrix could be made by solvent evaporation of a dispersion of the microencapsulated material. An example includes cellulose microcapsules dispersed in a polyvinyl acetate or alcohol water solution. A microencapsulated material to polymer ratio of 1 to 10 may be employed.

Regardless of whether the reducible dye and microencapsulated reducing agent are mixed with the polymeric film or provided as an overcoat thereon, the properties of each are such that upon application of heat above room temperature, the window 36 is capable of transforming from a non-transparent color to transparent. This transformation can occur when the chromofores in the molecular structure of the dyes that are responsible for the observed colors are reduced.

Advantageously, embodiments of the invention enable the reading of informational material contained inside a sealed envelope 10 behind the window 36 by heating the window 36 at a temperature above room temperature. The temperature should also be lower than which will ignite the envelope container and within the safety constrains of the apparatus capable of examining the envelope.

At room temperature, the window 36 typically has a dark color, which is based upon the selection of the dye/ink employed for the window 36. Upon heating, the window 36 will become colorless. The transformation from a dark or non-transparent color to transparent or colorless thereby exposes any informational material located underneath the window.

FIG. 4 shows the state of envelope 10 before heating window 36. As shown therein, window 36 displays a dark, non-transparent color. Thus, information 38 within the envelope 10, such as signatures, writings, barcodes, etc., are not visible from the exterior of the closed envelope prior to heating.

FIG. 5 shows the envelope 10 of FIG. 4 after heating window 36 with a heat source 40 to a temperature above room temperature, which transforms window 36 into a transparent window. Heat source 40 may include any suitable heat source, such as heating lamps.

The temperature at which window 36 is transparent may also be managed by, for example, using different passive films as thermal insulators or by adding IR or microwave absorbents to a polymer matrix of the film. Insulator elements could be also added to the polymer matrix, such as nano ceramic, air bubbles, etc. Examples of suitable potential designs are shown in FIGS. 6-7. More particularly, FIG. 6 shows a multilayer film 42 for window 36 comprising heat insulating layers 44 of any desired, suitable insulating material and thickness to regulate the transparency conversion temperature. FIG. 7 shows window 36 incorporating IR or microwave absorbents into the matrix. The performance of the layers will depend on the thermal absorption coefficient and optical transparence of the film, both of which may be modified depending upon the desired needs.

Advantageously, the reading of information 38 contained within a closed envelope 10 may be machine readable without human intervention, if desired. As shown in FIG. 5, a reading device 48 such as an optical imager, may be employed to read information 38 while, for example, the window 36 is still at an elevated temperature from heating. Alternatively, the information may be read by manually, for example. Advantageously, this read information could be transferred directly to a database for storage and analysis.

Thus, the information 38 contained within closed envelope 10 may remain private until it is desired to be read. There is also advantageously no need for use of a special pen or ink to write or print the inside material.

Moreover, although embodiments of the invention are particularly suitable for voting systems, as described above, they are also applicable to document management systems in general and other situations in which the user does not want to open the mail, but identify the information contained within the envelope and particularly underneath the envelope window.

Accordingly, embodiments of the invention advantageously solve the problem of how to read a closed envelope without opening the envelope. For example, embodiments of the invention include a method wherein the window of an envelope may include a mixture comprising a reducible dye and encapsulated bleach/strong base either as a film overcoat or as part of the polymer matrix of the film. The window will thus be the color of the selected dye or ink. The window may then be heated at a temperature above room temperature to make the film transparent. This temperature can be controlled by the selection of the encapsulated material. The material underneath the transparent window may be optically read while the film is at an elevated temperature. As this is an irreversible process in embodiments of the invention, the reading may be completed only once and thus this prevents the undesired, multiple processing of the same envelope and/or tampering with the covered film.

In accordance with another embodiment of the invention, envelope 10 comprises non-transparent window 36, which does not comprise a thin plastic or polymeric film comprising a reducible dye and a microencapsulated reducing agent either as part of an ink vehicle overcoated on the window film, or in the polymeric matrix of the window. Rather, window 36 may comprise a thermochromic film, as shown in FIG. 8. This embodiment functions similarly, as described above for the reducible dye/microencapsulated reducing agent embodiments. For example, at room temperature window 36 typically has a dark color, which is determined by the selection of the thermochromic material used therein. Upon heating, window 36 will become colorless or transparent. The transformation from a dark color to colorless allows the optical reading of the information 38 underneath the window 36.

FIG. 8 shows the state of envelope 10 before heating the window 36, which comprises a thermochromic material, to a temperature above room temperature to transform the window from non-transparent to transparent or colorless. As shown therein, window 36 displays a dark, non-transparent color before heating. Thus, information 38 within the envelope 10, such as signatures, writings, barcodes, other printed material, etc., are not visible from the exterior of the closed envelope prior to heating.

FIG. 9 shows the envelope 10 of FIG. 8 after heating window 36 with a heat source 40 to a temperature above room temperature, which transforms window 36 into a transparent window. Heat source 40 may include any suitable heat source, as described above.

The temperature at which window 36 becomes transparent may be controlled by, for example, using other films as insulators or by addition to the polymer matrix of IR or microwave absorbents. Insulator elements could be also added to the polymer matrix, such as non ceramic, air bubbles, etc. Examples of suitable potential designs are shown in FIGS. 10-11. More particularly, FIG. 10 shows a multilayer film 42 comprising heat insulating layers 44, as described above, to regulate the transparency conversion temperature. FIG. 11 shows window 36 incorporating IR or microwave absorbents into the matrix, as also described above.

An advantage of the afore-described embodiment employing a thermochromic window 36 is that thermochromic materials are both reversible and irreversible, depending upon the particular thermochromic material employed. Thermochromic materials suitable for use in embodiments of the invention are commercially available from sources such as Camel Chemical.

See also http://.colorchangematerial.com. Thermochromic pigments are reversible heat sensitive materials or organic dyestuff base, and are available in both aqueous slurry forms and powder forms. Color may be arranged, for example, according to the color change temperature range, as described below and shown in Table 1.

TABLE 1 Color Appears Color Disappears Type Darker Lighter Colorless 07 Below −5° C. 6° C. Over 5  1° C.  8° C. 10  8° C. 13° C. 15 12° C. 16° C. 17 14° C. 19° C. 20 16° C. 20° C. 25 22° C. 26° C. 30 24° C. 27° C. 33 27° C. 33° C. 36 32° C. 41° C. 45 40° C. 50° C. 47 44° C. 53° C. 52 52° C. 60° C.

Thermochromic Slurry

microcapsule particle: below 10 micron

thermochromic microcapsule 35%

application of binder: water soluble binder (acyl, urethane, rubber)

directions for use: 10% thermochromic slurry+water soluble binder 90%

package unit: 1 kg

Thermochromic Powder

microcapsule particle: below 10 micron

application of binder: oil based binder (acryl, urethane, epoxy, nylon)

directions for use: 5% thermochromic powder+binder 95%

package unit: 1 kg

Thermochromic Masterbatches

thermochromic powder 20%+resin 80%

kind of resin: PE, PP, PS, AS, PVC

directions for use: 3% thermochromic masterbatches+resin 97%

package unit: 25 ks

Slurries, powders and masterbatches may be incorporated by either mixing them with their polymeric vehicles and then film extrusion or film blowing.

FIGS. 12( a)-(b) shows an alternate approach using both irreversible and reversible thermochromic materials. More particularly, window 36 may be covered with a film comprising at least two layers. One of the layers 50 will become reversibly transparent upon heating to a first, lower temperature and another layer 52 will remain transparent at the first, lower temperature and will become irreversible colored at a second, higher temperature. Heating of the film at a temperature higher than room temperature will make the film transparent as the reversible layer 50 will convert to transparent. The information 38 underneath the window 36 may be read, preferably by an optical reader, while the film is at an elevated temperature. An increase in temperature can then change layer 52 to a colored film. Upon cooling, the window 36 will become inactive and not able to be read on a second read pass. On the first read pass, the window 36 can change from color to transparent to color. On the second read pass, the window 36 can remain this color regardless of the temperature. This is a clear indication of a tampered or read document. FIGS. 12( a)-12(b) schematically show the afore-described process using both irreversible and reversible thermochromic materials in a first read path (information visible and readable) and a second read path (information hidden and unreadable). U.S. application Ser. No. ______ entitled Method and System for Hiding Information (Attorney Docket G-291) discloses other suitable reversible and irreversible thermochromic materials, the contents of which are hereby incorporated by reference.

Thus, according to an embodiment, heat may be applied to read the information or mail. After cooling, the information is not visible. If heat is applied again, then the information is not readable. Heat will change the transparence only once. It is also noted that the apparatus used to read the information may employ color filters to increase the image contrast and facilitate reading.

It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims. 

1. A windowed envelope comprising: a first panel with an interior and an exterior side; a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope; and a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion, the envelope comprising thereon an adhesive layer on the interior side of the flap comprising an adhesive; wherein a non-transparent window is located on the first panel or the second panel, the window comprising a reducible dye and a microencapsulated reducing agent, which is adapted to irreversibly change to a transparent window upon heating the non-transparent window to a temperature above room temperature.
 2. The envelope of claim 1, wherein the dye and the reducing agent are included in an ink vehicle overcoated on the window.
 3. The envelope of claim 1, wherein the dye and the reducing agent are included in a polymeric matrix of the window.
 4. The envelope of claim 1, wherein the dye is selected from the group consisting of methylene green, methylene blue and rezasurin.
 5. The envelope of claim 1, wherein the reducing agent is bleach.
 6. The envelope of claim 1, wherein the reducing agent is a chemical base.
 7. The envelope of claim 1, wherein printed or written information is located inside the envelope behind the window.
 8. The envelope of claim 1, wherein the window is located on the second panel.
 9. The envelope of claim 1, wherein the window comprises two heat insulating layers with the window located therebetween and adjacent each heat insulating layer.
 10. The envelope of claim 3, wherein the polymeric matrix comprises at least one substance selected from the group consisting of IR absorbents, microwave absorbents, nano ceramics and air bubbles in the polymeric matrix.
 11. A method of detecting information located inside a closed envelope without opening the envelop comprising: providing a windowed envelope comprising: a first panel with an interior and an exterior side; a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope; and a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion, the envelope comprising thereon an adhesive layer on the interior side of the flap comprising an adhesive; wherein a non-transparent window is located on the first panel or the second panel, the window comprising a reducible dye and a microencapsulated reducing agent, which is adapted to irreversibly change to transparent upon heating the window to a temperature above room temperature; wherein information is located in the envelope behind the window; heating the window to a temperature above room temperature, wherein the window irreversibly changes from non-transparent to transparent thereby exposing the information located in the envelope behind the window.
 12. The method of claim 11 further comprising reading the information located in the envelope behind the window after the heating step.
 13. The method of claim 12, wherein the reading step comprises optically reading the information.
 14. The method of claim 12, further comprising transferring the read information to a database for storage.
 15. The method of claim 11, wherein the heating step comprises heating the window using a heat lamp.
 16. A windowed envelope comprising: a first panel with an interior and an exterior side; a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope; and a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion, the envelope comprising thereon an adhesive layer on the interior side of the flap comprising an adhesive; wherein a non-transparent window is located on the first panel or the second panel, the window comprising a thermochromic material, which is adapted to change to a transparent window upon heating the non-transparent window to a temperature above room temperature.
 17. The envelope of claim 16, wherein the window comprises two heat insulating layers with the window located therebetween and adjacent each heat insulating layer.
 18. The envelope of claim 16, wherein the window comprises a polymeric matrix with the thermochromic material located in the polymeric matrix, the polymeric matrix further comprising at least one substance selected from the group consisting of IR absorbents, microwave absorbents, nano ceramics and air bubbles.
 19. A method of detecting information located inside a closed envelope without opening the envelop comprising: providing a windowed envelope comprising: a first panel with an interior and an exterior side; a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope; and a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion, the envelope comprising thereon an adhesive layer on the interior side of the flap comprising an adhesive; wherein a non-transparent window is located on the first panel or the second panel, the window comprising a thermochromic material, which is adapted to irreversibly or reversibly change to transparent upon heating the window to a temperature above room temperature; wherein information is located in the envelope behind the window; heating the window to a temperature above room temperature, wherein the window changes from non-transparent to transparent thereby exposing the information located in the envelope behind the window.
 20. The method of claim 19, wherein the window comprises two heat insulating layers with the window located therebetween and adjacent each heat insulating layer.
 21. The method of claim 19, further comprising reading the information located in the envelope behind the window after the heating step.
 22. The method of claim 21, wherein the reading step comprises optically reading the information.
 23. The method of claim 21, further comprising transferring the read information to a database for storage.
 24. A method of detecting whether contents of a closed envelope have been read or tampered with comprising the steps of: providing a sealed, windowed envelope comprising: a first panel with an interior and an exterior side; a second panel attached to the first panel to define an interior portion having opposite side edges, a closed edge portion and an opening portion opposite the closed edge portion to provide access to the interior portion of the envelope; and a flap for sealingly adhering to an exterior surface of the first panel, the flap having an interior and an exterior side and attached to the second panel at an edge of the second panel opposite the closed edge portion, the envelope comprising thereon an adhesive layer on the interior side of the flap comprising an adhesive; wherein a window is located on the first panel or the second panel, the window comprising at least two layers each comprising a thermochromic material, wherein one of the layers is transparent at room temperature and another layer is non-transparent at room temperature; and then sequentially, heating the layers to a temperature above about 50 C and less than about 100 C, wherein both layers become transparent; and heating the layers to a temperature above about 100 C, wherein one of the layers is non-transparent and the other layer is transparent.
 25. The method of claim 24, further sequentially comprising: allowing the layers to reach about room temperature wherein both layers become non-transparent; heating the layers to between about 50 C and less than about 100 C; and heating the layers to a temperature above about 100 C wherein one of the layers is non-transparent and the other layer is transparent. 